1. Field of the Invention
The present invention relates to a stage apparatus for performing positioning by mounting an object, and particularly, to a stage apparatus suitably applicable to a semiconductor exposure apparatus. The invention also relates to an exposure apparatus using the aforementioned stage apparatus and a device manufacturing method for manufacturing a device, such as a semiconductor device, using such an exposure apparatus.
2. Description of the Related Art
FIG. 10 is a schematic diagram of a wafer stage of a conventional semiconductor exposure apparatus. Three translational axes (X, Y and Z directions) relative to a reference coordinate system and three rotational axes (xcex8x, xcex8y, xcex8z) around the three translational axes, respectively, will hereinafter be referred to as six degree-of-freedom positions.
In FIG. 10, reference numeral 41 represents a base supported on a floor F via dampers 51A and 51B; and 43 a Y-stage movable in the Y-direction on a reference plane on the base 41 by the action of a Y-linear motor 46 producing a thrust in the Y-direction along a fixed guide 42 fixed to the base 41. The base 41 and the fixed guide 42 are not in contact with the Y-stage 43, being connected by air pads 44a to 44c serving as static-pressure bearings. The Y-stage 43 has an X-direction guide, and guides X-stage 45 mounted on the Y-stage 43 in the X-direction. An X-linear motor stator producing a force in the X-direction is provided on the Y-stage 43 and drives, together with the X-linear motor movable part (rotor), the X-stage 45 in the X-direction. The base 41 and the X-guide are connected by an air pad serving as a static pressure bearing with the X-stage 45, and are not in contact therewith.
A tilting stage 48 is mounted on the X-stage 45. The tilting stage 48 travels in the Z-direction and rotates in the three rotational axes (xcex8x, xcex8y, xcex8z) directions by the thrust produced by a motor (not shown). A stage substrate 51 including a wafer chuck is mounted on the tilting stage 48 to hold a wafer 53, which is an object to be exposed. A measuring mirror for measuring positions in the X-direction and the Y-direction is provided on the stage substrate. (Only measuring mirror 49a for measuring in the X-direction and Y-direction is shown.)
The stage apparatus of a semiconductor exposure apparatus performs positioning using the six degree-of-freedom positions in the in-plane directions (X, Y, xcex8z) and in the vertical directions (Z, xcex8x, xcex8y), and performs exposure for a chip. Positions in the in-plane direction (X, Y, xcex8z) are measured with a laser interferometer 50 integral with a lens mirror cylinder (not shown). For positions in the tilting directions (Z, xcex8x, xcex8y), a position in the Z-direction and an angle of the rotational component are measured with an alignment measuring system (not shown), integral with the lens mirror cylinder.
In FIG. 10, the laser interferometer 50 is connected to the base 41 on the assumption that the lens mirror cylinder (not shown) is integral with the base 41. Although the measuring instrument for the Z-direction is omitted, it is possible to measure positions in the tilting directions (Z, xcex8x, xcex8y) by measuring three points on the substrate stage or the wafer from the lens mirror cylinder.
Positioning in the six-axis directions is accomplished by providing a servo system for each axis. Drive instruction values to a Y-direction linear motor and an X-direction linear motor serving as actuators for the X-direction and the Y-direction of the stage are calculated with a compensator on the basis of positional information of the laser interferometer 50 to drive the X-stage and the Y-stage, respectively. The tilting stage 48 is driven by calculating drive instruction values by the compensator to an actuator for the tilting stage 48 in response to measured values of the Z-direction position, the angles in the rotating directions (xcex8x, xcex8y) and in the xcex8z-direction.
It is thus possible to control the six degree-of-freedom positions of the three translational axes (X, Y, Z) and the three rotational axes to arbitrary positions relative to the lens mirror cylinder serving as a reference point of the stage, thus permitting highly accurate positioning.
In the stage apparatus of such a semiconductor exposure apparatus, a high positioning accuracy is required because of a high resolution of the line width to be exposed. Also, the semiconductor exposure apparatus, being production equipment, is required to provide a high throughput. In order to satisfy this requirement, it is necessary to have a high response of the servo system of the stage, and to be capable of traveling at a high speed. In order to improve the response of the servo system, the mechanical system of the stage must have a high rigidity. With a low rigidity of the stage, it is impossible to improve the band of the servo system, and inability to rapidly respond to a target position decreases throughput. A low band of the servo system results in a decrease in the ability to inhibit disturbances, and makes it impossible to accomplish highly accurate positional control.
The aforementioned conventional stage is composed of a base supporting the entire stage apparatus, a Y-stage conducting travel in the Y-direction, an X-stage conducting travel in the X-direction, a tilting stage conducting travel in the tilting direction and a substrate stage for holding a wafer, these stages forming a unit, thus leading to a lower mechanical rigidity. This arrangement, however, creates a resonance point determined by the rigidity of air portions connecting these stages and the mass of the configuration. The stage system, therefore, has a servo band restricted by this resonance point, and cannot improve response.
The present invention has an object to provide a high-speed and high-accuracy stage apparatus having a wide servo band by achieving a higher resonance point of the mechanical system thereof in a simple configuration with a positionally controllable stage.
The stage apparatus includes a base having a reference plane, a stage mounted on the base, a plurality of static-pressure bearings forming a gap between the reference plane and the stage, a plurality of preloading mechanisms producing a preload between the stage and the reference plane, a guideless motor for driving the stage, and a controller for controlling driving of the stage in (i) at least one of a direction perpendicular to the reference plane and in a tilting direction by controlling at least one of the static-pressure bearings and the preloading mechanism, and (ii) in an in-plane direction by the use of the guideless motor.
The above-mentioned stage should preferably have a monolithic structure.
It is desirable to control positions in the direction perpendicular to the reference plane of the stage and in the tilting direction by controlling the preloading mechanism.
In another aspect, the present invention provides an exposure apparatus that includes a base having a reference plane, a stage mounted on the base, a plurality of static-pressure bearings forming a gap between the reference plane and the stage, a plurality of preloading mechanisms producing a preload between the stage and the reference plane, a guideless motor for driving the stage, a controller for controlling driving of the stage in (i) at least one of a direction perpendicular to the reference plane and in a tilting direction by controlling at least one of the static-pressure bearings and the preloading mechanism, and (ii) in a direction within the reference plane by the guideless motor, and an exposure apparatus for exposing a device held by the stage.
In yet another aspect, the present invention provides a device manufacturing method that includes providing a base having a reference plane, mounting a stage on the base, forming a gap between the reference plane and the stage by a plurality of static-pressure bearings, producing a preload between the stage and the reference plane by a plurality of preloading mechanisms, driving the stage by a guideless motor, controlling, using a controller, driving of the stage in (i) at least one of a direction perpendicular to the reference plane and in a tilting direction by controlling at least one of the static-pressure bearings and the preloading mechanism and (ii) in a direction within the reference plane by the guideless motor, and exposing a wafer, mounted on the stage, to a pattern on a mask to produce a device.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.